Bovine Respiratory Disease test a step closer

22 June 2018

The development of a precise, objective method of diagnosing Bovine Respiratory Disease (BRD) in Australian feedlot cattle through a blood test is progressing, with preliminary results from an MLA and ALFA research project showing a high degree of accuracy in identifying the disease.

BRD is the leading cause of morbidity and mortality in Australian feedlot cattle.

The project, Metabolomics of Bovine Respiratory Disease, has been identifying BRD using a diagnostic tool known as metabolomics and is being led by Associate Professor Luciano González from University of Sydney.

The researchers set out to explore changes that occur in the blood composition of animals with the onset of disease in the search for biomarkers to objectively define BRD cases.

The methodology behind metabolomics

Associate Professor González said the project confirmed that BRD could be identified using metabolomics, which is a field of science examining the metabolite profile of body tissues and fluids.

“We worked with a commercial feedlot in NSW and the trial involved 898 head of cattle, reflecting a mix of different breeds from different backgrounds,” Associate Professor González said.

PhD student Claudia Blakebrough-Hall explained the methodology.

“We took blood tests at induction and then again any time an animal was identified by pen riders as showing visual signs of BRD,” Claudia said.

“Cattle with visual symptoms were removed from the pen, and for every sick animal pulled, a visually healthy animal was also removed so we could compare blood results, lung auscultation scores and rectal temperatures.

The project examined blood samples from both sick and healthy animals to discover informative biomarkers.

Researchers identified 12 different biomarkers in total that were associated to different clinical observations, but were able to determine a sick animal in the early stages of the illness with 85% accuracy. This was completed using just one biomarker on independent datasets which were not used in the initial search of biomarkers.

All animals were followed throughout the supply chain to slaughter, to measure the incidence of lesions, adhesions and abscesses in the lungs to see if there was any evidence an animal had BRD. Other carcase information was also collected.

“The trial demonstrated that when cattle became sick, it changed their metabolites in ways we expected. The composition of the blood of sick cattle reflected the visual changes the pen rider observed,” Claudia said.

Scope for further research

Associate Professor González said there was scope to undertake more research that could possibly lead to the development of a simple crush-side test to help lot feeders diagnose BRD.

“Other research that could lead from this trial includes examining what are the metabolomic changes of an animal going through the disease process,” Associate Professor González said.

“This would help us understand the science of disease development and refine therapeutic and treatment protocols.

“We would also like to trial prediction models and biomarkers in different feedlots in other parts of Australia.”